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Kerry Matthews

Qld Mining Acts & Regulations - GDA

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Anybody aware of who will be driving the changes to the Qld Coal Mining Safety and Health Regulation 2001 regard reference to "GDA" now that we are close to having two "GDA's"?

CoalMinSHR01 only references the term "GDA" without any reference to which "GDA" it is which in the past was fine as there was only GDA94. Even the legislation's dictionary section only provides a definition regard GDA (means the Geocentric Datum of Australia which is a system of earth-centred datum used for mapping)

Now Recognised Standard 10 made under the Coal Mining Safety and Health Act 1999 does specifically refer to GDA94 (as such) but this does conflict with the Regulations (which makes no reference at all to GDA94) and where a part of a standard conflicts with the Act or the Regulations then the Act or Regulations takes precedence. Since the Regulations only make reference to "GDA" and we will now have GDA94 and GDA2020 then we have a problem with the regulations.         

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Hi Kerry,

Any legislative changes will be driven by the jurisdiction to which it applies; in this case, the Queensland Government.  The Queensland Government will need to review its legislation and apply the appropriate amendments.  There is a Queensland Government representative on the GDA Modernisation Implementation Working Group, who will help in this activity.

You have highlighted the GDA reference defined within the regulation as “GDA means Geocentric Datum of Australia which is a system of earth-centred datum used for mapping.”

I must preface my comments by stating that I am not providing a legal opinion.

The current Recognized-value standard of measurement of position 2012 (No.1) provides the definition of GDA as (https://www.legislation.gov.au/Details/F2012L00800):

“The Geocentric Datum of Australia is realised by the coordinates of the following Australian Fiducial Network geodetic stations referred to the GRS80 ellipsoid determined within the International Earth Rotation Service Reference Frame 1992 (ITRF1992) at the epoch 1994.0”

When this was published, there was only one Geocentric Datum of Australia, as the earlier reference system was named the Australian Geodetic Datum and there was no need to distinguish them by adding their respective year of coordinate realisation.

The soon to be adopted Recognized-value standard of measurement of position 2017 will need to distinguish between the GDA at the 1994.0 epoch from the new GDA at the 2020.0 epoch.  This will be the case – the definition will be “Geocentric Datum of Australia 2020”.
 

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Thanks Dan, Just a comment on the Australian Geodetic Datum which there was two, AGD66 & AGD84, both were based on the same spheroid etc with one essentially an updated Readjustment of the other with shifts of 1-3 metres so there definitely was and still is a need to differentiate these pair. Unlike around 1975 when AGD66 was legislated by the Qld mines department who provided the baseline control into most mine sites at the time so as to ensure sites adopted AGD66, this never occurred with AGD84 or GDA94 for that matter.

Today there are still 40-50 year old mine sites operating on AGD66, which never moved or adopted AGD84 and only have a reference to GDA94. Those sites that simply state their datum is AGD/AMG is technically & physically incorrect.

Wonder if the legislators take the opportunity to mandate GDA2020 this time around :)   

 

Edited by Kerry Matthews
This forum doesn't like the word ****? ****-adjustment becomes ****-adjustment? (Readjustment)
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Yes, thanks Kerry.  Quite right.  Interestingly, AGD66 was only used as an identifier after AGD84 was released.  The biggest changes from AGD66 to AGD84 were in northern Queensland, with over 5 metres shift.  I'm sure that this wont be the case between GDA94 and GDA2020.

I enjoy reading old geodetic papers.  Here's one that you might like to read too. The Geodetic Adjustment of Australia, 1963-1966 by A. G. Bomford.  There is a great quote in this paper:

"Surveyors are paid to get the right answer and the wrong answer scores nought; yet the only man who can be quite certain of making no mistakes is the man who says nothing and does nothing."

So thanks for posting and keeping us all well informed.

 

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